Many gas turbine engine platforms include a centrifugal compressor or “impeller” positioned upstream of the engine's combustion section. An impeller typically includes a generally annular disk and a plurality of blades, which extend outward from the annular disk and which wrap tangentially around the disk in a twisting or spiral pattern. The impeller blades serve as airfoils and, during rotation of the impeller, force high pressure airflow from the impeller's forward or inducer portion to the impeller's aft or exducer portion. As airflow travels from the inducer portion to the exducer portion under the influence of centrifugal forces, the air is compressed and its pressure increased. Hot, compressed airflow is expelled by the impeller's exducer portion in a radially-outward direction and supplied to the gas turbine engine's combustion section, mixed with fuel, and ignited to produce combustive gases. The combustive gases are then directed through one or more air turbines downstream of the combustion section to produce power and to drive further rotation of the impeller.
An impeller is typically exposed to considerable temperature gradients and centrifugal forces during engine operation. Advancements in impeller design, cooling, and materials have brought about significant improvements in impeller temperature tolerances. Nonetheless, impellers remain prone to physical deformation at higher engine speeds and operating temperatures. For example, during engine operation, a condition referred to as “flowering” can occur wherein the impeller's exducer portion deflects in a forward direction such that the back disk and the outer blade ends close inwardly toward the impeller centerline in a manner somewhat similar to the petals of a closing flower. While flowering is a temporary condition occurring while the impeller is operating at high temperatures and under significant centrifugal loads, flowering can be highly problematic. Specifically, flowering can degrade allotted clearances and potentially result in rubbing between the impeller and the surrounding static infrastructure of the engine, such as a shroud positioned around the impeller. Over time, the forward-biased deformation of the impeller can become permanent, a condition referred to as “axial creep.” Axial creep can culminate in the gradual forward movement or “walking” of the impeller over its service life, which may again reduce allotted engine clearances, result in undesired friction between engine components, or otherwise negatively impact engine performance.
It is thus desirable to provide impellers having an increased resistance to deformation (flowering and axial creep) when subjected to highly elevated temperatures and rotational speeds characteristic of gas turbine engine applications. Ideally, such a deformation-resistant impeller could be produced in a relatively straightforward and cost effective manner utilizing conventionally-known manufacturing techniques. It is also desirable to provide embodiments of a gas turbine engine containing such a deformation-resistant impeller and, perhaps, having a reduced length and weight. Other desirable features and characteristics of the present invention will become apparent from the subsequent Detailed Description and the appended Claims, taken in conjunction with the accompanying Drawings and the foregoing Background.